The present invention relates to a direct-current electric motor and a method of manufacturing this motor.
It applies in particular to electronic-commutation electric motors used particularly in electric fan units equipping motor vehicles.
A direct-current electric motor is already known in the state of the art, of the type including an armature winding with an armature of generally cylindrical shape carrying conducting coils distributed into three phases and into at least two layers, the coils of the same phase being supplied with electricity simultaneously, each phase including at least two pairs of diametrally opposed coils.
The armature winding is, for example, of the three-phase square type including twelve coils distributed into the three phases, the coils of one phase being supplied with electricity simultaneously. Each phase includes two pairs of diametrally opposed coils. Each pair of coils of one phase is arranged at a right angle with respect to the other pair of coils of this phase.
In a conventional way, the coils are wound on the armature winding by distributing them into three successive layers corresponding to the three phases of the armature winding.
The winding of the armature is carried out by means of a winder including an arm intended to wind the conductors forming the coils on the armature. The arm successively winds the four coils of the lower layer (first phase), then the four coils of the intermediate layer (second phase) and finally the four coils of the upper layer (third phase). The four coils of the same phase are linked electrically in series. The coils of the different phases are spaced by 30.degree. from each other.
Because the different phases of the armature winding correspond to superimposed layers of coils, the lengths of the conductors constituting the phases are different. This results in different phase resistances and electrical imbalance which is particularly troublesome when the power supply to and the commutation of the phases is carried out by an electronic circuit.